1. Field of the Invention
The present invention generally relates to a semiconductor technique and more particularly to a method for forming on a semiconductor substrate a silicon-containing insulation film having high resistance to diffusion by using a plasma CVD (chemical vapor deposition) apparatus. The present invention also relates to a method of fabricating a semiconductor device.
2. Description of the Related Art
As semiconductors have progressed to accommodate a demand for high speed and high density in recent years, a reduction of capacitance between lines is required to avoid signal delays in the multi-layer wiring technology field. Because a reduction in the dielectric constant of a multi-layer wiring insulation film is required in order to reduce the capacitance between lines, insulation films having low dielectric constants have been developed.
Conventionally, a silicon oxide (SiOx) film is formed by adding oxygen (O2), nitric oxide (NO) or nitrous oxide (N2O) as an oxidizing agent to a silicon source gas such as SiH4 and Si(OC2H5)4, and applying heat or plasma energy to the source gas. A dielectric constant (∈) of this film was approximately 4.0.
By contrast, by using a spin-coat method using inorganic silicon oxide glass (SOG) materials, a low dielectric constant insulation film having a dielectric constant (∈) of approximately 2.3 was formed.
By using a plasma CVD method with CxFyHz as a source gas, a low dielectric constant fluorinated amorphous carbon film having a dielectric constant (∈) of approximately 2.0 to 2.4 was formed. Further, by using a plasma CVD method using a silicon-containing hydrocarbon (for example, P-TMOS (phenyltrimethoxysilane) as a source gas, a low dielectric constant insulation film having a dielectric constant (∈) of approximately 3.1 was formed. Additionally, by using a plasma CVD method using a silicon-containing hydrocarbon having plural alkoxy groups as a source gas, a low dielectric constant insulation film having a dielectric constant (∈) of approximately 2.5 was formed when optimizing film formation conditions.
However, the above-mentioned conventional approaches have the following problems:
In the case of the inorganic SOG insulation film formed by the spin-coat method, there are problems in that the materials properties are not distributed equally on a silicon substrate and that an apparatus used for a curing process after coating the material is expensive.
In the case of the fluorinated amorphous carbon film formed by the plasma CVD method using CxFyHz as a source gas, there are problems such as low heat resistance (370° C. or lower), poor adhesion with silicon materials, and low mechanical strength of the film formed.
Furthermore, among silicon-containing hydrocarbons, when P-TMOS is used, a polymerized oligomer cannot form a linear structure such as a siloxane polymer because P-TMOS contains three alkoxy groups. Consequently, a porous structure is not formed on a silicon substrate, and hence a dielectric constant cannot be reduced to a desired degree.
When a silicon-containing hydrocarbon containing plural alkoxy groups is used, a polymerized oligomer can form a linear structure such as a siloxane polymer by optimizing film formation conditions. Consequently, a porous structure can be formed on a silicon substrate and a dielectric constant can be reduced to a desired degree. However, there are problems in that for a porous structure, a gas, a solvent and an atom/ion, etc. (metals such as Cu, and nitrogen, etc.) can easily diffuse into the film.